src/core/lib/promise/join.h

// Copyright 2021 gRPC authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef GRPC_CORE_LIB_PROMISE_JOIN_H
#define GRPC_CORE_LIB_PROMISE_JOIN_H

#include <grpc/support/port_platform.h>

#include "absl/meta/type_traits.h"

#include "src/core/lib/promise/detail/basic_join.h"

namespace grpc_core {
namespace promise_detail {

struct JoinTraits {
  template <typename T>
  using ResultType = absl::remove_reference_t<T>;
  template <typename T, typename F>
  static auto OnResult(T result, F kontinue)
      -> decltype(kontinue(std::move(result))) {
    return kontinue(std::move(result));
  }
  template <typename T>
  static T Wrap(T x) {
    return x;
  }
};

template <typename... Promises>
using Join = BasicJoin<JoinTraits, Promises...>;

}  // namespace promise_detail

/// Combinator to run all promises to completion, and return a tuple
/// of their results.
template <typename... Promise>
promise_detail::Join<Promise...> Join(Promise... promises) {
  return promise_detail::Join<Promise...>(std::move(promises)...);
}

}  // namespace grpc_core

#endif  // GRPC_CORE_LIB_PROMISE_JOIN_H